h3{
    color: brown;
    text-align:center;
}
.button{
    height: 25px;
}
select{
    height: 20px;
    margin:0 10PX ;
}
header{
    display: flex;
    justify-content:center;
}
input{
    height:15px;
    margin:0 10px;
}
table#stu{
    width: 100%;
    height: 100%;;
    align-content:center;           
    border: 2px solid black;
}
table#stu tr{
    height: 50px;
}
table#stu tr td{
    border: 1px solid #877777;
    text-align:center;
}